Rectifier device



Aug. 29, 1933. A. B. DU MONT RECTIFIER DEVICE Filed Nov. 26, 1928 awue/wbm Am BlJu/"lonf 351 /75 W 5 Patented Aug. 29, 1933 PATENT OFFICE RECTIFIER DEVICE Allen B. Du'Mont, Bloomfield, N. J., assignor to De Forest Radio Company, Jersey City, N. J., a corporation of Delaware Application November 26, 1928 Serial No. 321,845

6 Claims. (Cl. 175--363) This invention relates in general to rectifying devices.

Oneof the objects of this invention is the provision of a -nove1 construction of rectifier device 5 ofthe'vacuum tube or electron discharge type in which the plate or anode is made of a helical coil of wire.

A further object ,of this invention is the construction of a deviceof this type in which the IQ anode is made in coiled form to permit heat dissipation and hence prevent back emission.

A further object of this invention is the construction of an anode of the above type for rectb fier' devices which may be more readily freed of gas, whichis cheaper and easier to manufacture and which is adapted to. be made of molybdenum or tungsten wire.

A further object of this invention is the construction of a rectifying device in accordance with the. principles of this invention whichis capable of greatly increasing the output over what is normally secured.

A further object of this invention is the construction of arectifier device having two grid 25. like anodes .wound'concentrically-with a higher voltage on the outer grid totake care of the addition of. voltage drop and hence permit a great increase in the output of the device.

. Another objectof theinvention is to provide a rectifier. tube of the type'employing a central electron emitting cathode and a plurality of concentrically surrounding electrodes in conjunction with circuit arrangements for impressing upon the inner electrodea potential with respect to the cathode which is diiferent from the potential on the other electrodewith respect to the cathode. As a result of this feature the inner electrode may have applied thereto an average positiveipotential with respect to the cathode which is lower than the average positive potential ap ,plied to the other electrode with respect to the cathode.

These and other objects as will appear from the following disclosure are secured by means of 45. this invention. i I

This invention resides substantially in the combination, construction, arrangement, relative location of parts and circuital connections, all as will appear more fully hereinafter;

Referring to the drawing Figure 1 is a diagrammatic illustration of'the usual form of rectifier device now known employing a continuous plate anode.

Y Fig. 2 is a diagrammatic illustration of one form of the device of this invention.

Fig. 3 is a diagrammatic illustration of another form of the device showing the circuit connections thereto, for employment as a full wave rectifier.

Fig. 4 is a view of the device of Fig. 3 showing another circuit connection thereto for use as a half wave rectifier.

In the usual forms of half and full wave rectifiers a carbonized plate is used in conjunction with a cathode of either the oxide coated or thoriated tungsten type. The plate is carbonized to make it a black body and, hence, a good radiator so as to reduce as much as possible back emission which results when the rectifier is operated at full output causing the plate to overheat. This production of what is termed back emission is particularly troublesome when an oxide coated cathode is used since there is always a possibility that some of the coating will get on the plate. causing it to throw off electrons at a much lower temperature than it would were there no oxide coating on it. Carbonizing the plate electrodes is a troublesome and expensive process and the presence of the carbonized plates within the vessel to. be exhausted makes it diflicult of exhaustion.

Instead of carbonizing the plate electrode to radiate more heat and tend to keep it cool, according to the principles of this invention the plate is made in the form of a helical coil or winding of fine wire which permits the heat to radiate directly through the spaces between the turns of the coil. A grid of this type can be more readily treated to free it from gas which facilitates the process of manufacture. vThe general practice now is to manufacture the plates of nickel because of its cheapness and not because of any desired electrical characteristics. The most ideal,- practical, ordinary metal for these plates is molybdenum or tungsten. However, whereas a plate of nickel would only cost a few cents, a plate of molybdenum or tungsten would cost several dollars, with the further disadvantage that these metals, even when produced in plate form, are very hard to work. However, when the anode is made in the form of a helical coil of wire in accordance with the principles of this invention it is possible to employ molybdenum or tungsten wire since wire of these metals can be easily and cheaply made. Furthermore these metals are highly desirable from both a mechanical and electrical standpoint and, in addition, are more easily gas freed and have a high melting point. With this construction then the output of the rectifier 110 tube is not limited by plate heating as is the case when a plate of solid construction is employed. Furthermore, by using two concentrically wound coils and applying a higher voltage to the outer coil to take care of voltage drop it is possible to double or treble the output of the tube. This same idea can be used in three element tubes.

In order to get a clear understanding of this invention the usual form of rectifier tube is shown in Fig. 1 with the exhausted vessel at 1 having the re-entrant stem tube 2 in which are support ed the wire supports 8 and 9 upon which the plate electrode 6 is grounded. This plate electrode is usually cylindrical in form and is often closed at the upper end to provide a sort of thirnble construction. The cathode is shown at 4 within the plate 6. The lead wires 5 carry the current to the cathode and the lead wire 7 is connected to the anode. It is at once apparent that the heat generated by the cathode 4 goes directly to the plate and tends to heat it to a high temperature which effect is partially overcome by carbonizing the plate to make it a good radiator of heat. Even with this precaution there is considerable production of back emission by reason of the heating of the plate and a resultant decrease in the effective current output.

A rectifier tube constructed in accordance with this invention is shown in Fig. 2 comprising the exhausted vessel 10 having the re-entrant stem tube 11 on which are supported the wires 12 and 13 around which are wound the wire turns of the plate electrode 14. The cathode is shown at 15 having the leads 16 extending exteriorly of the a vessel and a lead 17 is provided for the plate electrode. With this construction it is possible to use molybdenum or tungsten wire and due to the open construction of the plate radiation of heat directly to the walls of the vessel is possible.

This same device may take the form in Fig. 3 in which the exhausted vessel is shown at 10 having the re-entrant stem tube 11 on which are supported the wires 12 and 13. The helical wire coil is shown at 14. A second helical wire coil 20 is shown concentric with and inside the wire coil 14. The coil 20 is wound around the supports 18 and 19 secured in the press of the stem tube 11. The cathode is shown at 15 having its terminals connected to the secondary 30 of a transformer which may be supplied with energy from any suitable alternating current source. The coils 14 and 20 are provided with the leads 17 and-18 which are connected to the ends of an inductance 19 which inductance can be a part of the transformer which includes coil 30, if this be desired. The output leads'21 and 20 may be connected to adjustable taps on the coils 30 and 19 respectively. A filter is placed in these leads and comprises as an illustrative example the condensers 22 and 24 and the inductance 23. The terminals 25 represent the output terminals of the device to which any desired load may be connected. In this device the number of turns on the two grids can be varied so the currentto each anode is the same. By means of the adjustable connection to the transformer 19 the average positive potentials of the inner grid 20 with respect to the cathode 15 may be less than the average positive potentials applied to the grid 14 with respect to the cathode 15. Thus when the voltage in the winding 19 is such as to render the grid 14 positive with respect to the cathode 15, the grid 201s negative with respect to the cathode 15. Nevertheless, this negative potential on the grid 20 may be compensated for by the high positive potential on the grid 14. On the other hand, when the current is such as to render the grid 20 positive, its positive potential with respect to the cathode is less than was the positive potential of the grid 14 with respect to the cathode. In other words, by means of the adjustable connection to the transformer 19 the current from the cathode to the two anodes may be equalized, notwithstanding the fact that one anode is nearer to the cathode than the other. With this arrangement, therefore, there is provided a full wave rectification with means for adjusting the currents to the two anodes to any desired ratio, namely by the adjustable connection to the transformer 19.

The vacuum rectifying device of Fig. 4 is the same as that in Fig. 3, but the external connections thereto are different. In this case the cathode 15 is heated from the secondary 30 of a. transformer as before Coil 14 is connected by a wire 17 to one terminal of the secondary 19 of the transformer. The coil 20 is connected by a wire 18 to an adjustable tap on the coil 19.

'The other terminal of coil 19 is connected to the filter as before and the wire 21 is connected to the filter and an adjustable tap on the coil 30. The output terminals 25 of the filter, as

before, provide the point to which the load is connected. In this arrangement by means of the adjustable tap connected to the wire 18 and coil 19 it is possible to vary the voltage applied to the inside grid or coil 20 so that it is lower than the voltage applied to the outside coil or grid 14. This provides an additional source of energy by means of which the flow of electrons to the outside grid 14 may be in creased.

It will at once be apparent from the foregoing disclosure that I have provided a device which operates in accordance with new principles and while I have shown embodiments of this device in the drawing I do not wish to be limited thereto, but rather to these principles and their scope as defined in the appended claims. For instance, this invention may just as readily be applied to a full wave rectifier as to a half wave rectifier.

What I seek to secure by United States Let ters Patent is:

1. In a combination as described, an evacuated vessel, an electron emitting cathode supported within said vessel, two concentric helically wound anodes within said vessel adjacent said cathode to receive electrons emitted therefrom, a source of energy connected to said cathode, means for impressing potentials of different value on said electrodes so that the outer electrode is always at a higher potential when the device is conducting, and circuit connections between said cathode and said electrodes including a filter to provide the output circuit thereof.

2. In combination an electric discharge device comprising an exhausted vessel, an electron emitting cathode, a plurality of anodes situated at different distances from said cathode at least one of said anodes being in the form of a helically wound wire. means for impressing alternating currents to be rectified across said anodes and cathode, said means serving to maintain said anodes always at difierent potentials with respect to said cathode when the device is conductive.

3. The combination according to claim 2 in which said anodes are subjected to different potentials.

which the respective average anode potentials are in proportion to their distance from the cathode.

6. The combination according to claim 4 in which said anodes are in the form of wound grids, the anode nearer the cathode having a pre-determined number of turns with respect to the number of turns on the other anode so that the electron streams to both anodes are substantially equal.

ALLEN B. DU MONT. 

